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Articles 1 - 6 of 6
Full-Text Articles in Earth Sciences
Microbial Nanowires: Is The Subsurface "Hardwired"?, Dimitrios Ntarlagiannis, Estella A. Atekwana, Eric A. Hill, Yuri A. Gorby
Microbial Nanowires: Is The Subsurface "Hardwired"?, Dimitrios Ntarlagiannis, Estella A. Atekwana, Eric A. Hill, Yuri A. Gorby
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
The Earth's shallow subsurface results from integrated biological, geochemical, and physical processes. Methods are sought to remotely assess these interactive processes, especially those catalysed by micro-organisms. Using saturated sand columns and the metal reducing bacterium Shewanella oneidensis MR-1, we show that electrically conductive appendages called bacterial nanowires are directly associated with electrical potentials. No significant electrical potentials were detectable in columns inoculated with mutant strains that produced non-conductive appendages. Scanning electron microscopy imaging revealed a network of nanowires linking cells-cells and cells to mineral surfaces, "hardwiring" the entire length of the column. We hypothesize that the nanowires serve as conduits …
Blue Nile Incision On The Ethiopian Plateau: Pulsed Plateau Growth, Pliocene Uplift, And Hominin Evolution, Nahid D.S. Gani, M. Royhan Gani, Mohamed G. Abdel Salam
Blue Nile Incision On The Ethiopian Plateau: Pulsed Plateau Growth, Pliocene Uplift, And Hominin Evolution, Nahid D.S. Gani, M. Royhan Gani, Mohamed G. Abdel Salam
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
The 1.6-km-deep Gorge of the Nile, a rival of the Grand Canyon, resulted from the deep incision of the Blue Nile drainage into the uplifted Ethiopian Plateau. Understanding the incision history of the plateau is crucial to unraveling the Cenozoic tectonoclimatic evolution of the region, particularly because the region has long been used as a natural laboratory to understand the geodynamics of continental rifting and the evolution of hominins. We undertake a quantitative geomorphologic approach integrating field, geographic information system (GIS), and digital elevation model (DEM) data to analyze incision (volume, long-term rates, and spatiotemporal variability) and river longitudinal profiles …
The Microbial Community Structure In Petroleum-Contaminated Sediments Corresponds To Geophysical Signatures, Jonathan P. Allen, Estella A. Atekwana, Eliot A. Atekwana, Joseph W. Duris, D. Dale Werkema, Silvia Rossbach
The Microbial Community Structure In Petroleum-Contaminated Sediments Corresponds To Geophysical Signatures, Jonathan P. Allen, Estella A. Atekwana, Eliot A. Atekwana, Joseph W. Duris, D. Dale Werkema, Silvia Rossbach
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
The interdependence between geoelectrical signatures at underground petroleum plumes and the structures of subsurface microbial communities was investigated. For sediments contaminated with light non-aqueous-phase liquids, anomalous high conductivity values have been observed. Vertical changes in the geoelectrical properties of the sediments were concomitant with significant changes in the microbial community structures as determined by the construction and evaluation of 16S rRNA gene libraries. DNA sequencing of clones from four 16S rRNA gene libraries from different depths of a contaminated field site and two libraries from an uncontaminated background site revealed spatial heterogeneity in the microbial community structures. Correspondence analysis showed …
Sedimentology Of Acid Saline Lakes In Southern Western Australia: Newly Described Processes And Products Of An Extreme Environment, Kathleen Counter Benison, Brenda Beitler Bowen, Francisca Oboh-Ikuenobe, Elliot A. Jagniecki, Deidre A. Laclair, Stacy L. Story, Melanie R. Mormile, Boyoung Hong
Sedimentology Of Acid Saline Lakes In Southern Western Australia: Newly Described Processes And Products Of An Extreme Environment, Kathleen Counter Benison, Brenda Beitler Bowen, Francisca Oboh-Ikuenobe, Elliot A. Jagniecki, Deidre A. Laclair, Stacy L. Story, Melanie R. Mormile, Boyoung Hong
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Naturally acid saline systems with pH values between 1.7 and 4 are common on the Yilgarn Craton of southern Western Australia. a combination of physical and chemical processes here yield a previously undescribed type of modern sedimentary environment. Flooding, evapoconcentration, desiccation, and eolian transport at the surface, as well as influx of acid saline groundwaters, strongly influence these lakes. Halite, gypsum, kaolinite, and iron oxides precipitate from acid hypersaline lake waters. Shallow acid saline groundwaters affect the sediments of the lakes and associated mudflats, sandflats, channels, and dunes by precipitating early diagenetic halite, gypsum, iron oxides, clays, jarosite, and alunite. …
Extinction Pattern Of Reef Ecosystems In Latest Permian, Yasheng Wu, Jiasong Fan, Hongxia Jiang, Wan Yang
Extinction Pattern Of Reef Ecosystems In Latest Permian, Yasheng Wu, Jiasong Fan, Hongxia Jiang, Wan Yang
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Studies of two Permian-Triassic boundary (PTB) sections on top of a Changhsingian reef in Ziyun, Guizhou Province, southwestern China indicate that the end-Permian mass extinction of reef ecosystems occurred in two steps. The first step is the extinction of all stenotropic organisms such as calcisponges and fusulinids in the latest Permian (in the Clarkina yini conodont zone). The biota after the first extinction is simple, comprising eurytropic organisms including microgastropods, ostracods, and some small burrowing organisms, or only algal mats. At the beginning of the Early Triassic (i.e. the beginning of the Hindeodus parvus zone), the environments became anoxic, and …
Percussive Penetration Of Unconsolidated Granular Media In A Laboratory Setting, Leslie S. Gertsch
Percussive Penetration Of Unconsolidated Granular Media In A Laboratory Setting, Leslie S. Gertsch
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
This controlled study examined the feasibility of a simple percussive approach to drilling through unconsolidated regolith deposits on Mars. The experiments showed that the approach is feasible at the low power levels and low confining pressures used, and that the rate of impact is more important to the penetration rate than is the mass of the impactor (hammer). More massive impactors tend to lower energy efficiency, as they do in terrestrial pile-driving. Unexpectedly, penetration plotted against applied energy tends to cluster into parallel linear trends. Within a given cluster, penetration is very sensitive to applied energy, while between clusters, the …